In 2006, four sex workers were found dumped in a ditch near Atlantic City's border. The serial killer has yet to be identified.

Serial killers have long targeted prostitutes—from Jack the Ripper, an uncaught murderer who terrorized women in late 19th-century London, to the Long Island Serial Killer, an uncaught murderer whose last confirmed victim disappeared in September 2010 after advertising sex work on Craigslist. We explore the various reasons why serial killers prey upon sex workers.

Before they're caught, serial killers often fly under-the-radar. But just because police and the public aren't aware of a killing spree, doesn't mean it isn't happening. We look at five unsolved serial killer cases, the murders connected to them and some of the information we do (and don't) know.

It's been nearly a decade since four bodies were discovered spread over a quarter of a mile stretch of beach in Long Island, New York. Since then, other remains have been found, with 10 victims or more now likely tied to a single perpetrator.

Peter Vronsky, author and investigative historian, speaks with us about ancient killers, the influence of technology on crime and how, in 100 years, the Long Island Serial Killer could be the new Jack the Ripper.